Explosives

An explosive material, also called an explosive, is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An explosive charge is a measured quantity of explosive material.

This potential energy stored in an explosive material may be

chemical energy, such as nitroglycerine or grain dust

pressurized compressed gas, such as a gas cylinder or aerosol can

nuclear energy, such as in the fissile isotopes uranium-235 and plutonium-239

pyrotechnic compounds as found in gas pressure blasting devices and fireworks

Explosive materials may be categorized by the speed at which they expand. Materials that detonate (explode faster than the speed of sound) are said to be "high explosives" and materials that deflagrate are said to be "low explosives". Explosives may also be categorized by their sensitivity. Sensitive materials that can be initiated by a relatively small amount of heat or pressure are primary explosives and materials that are relatively insensitive are secondary explosives.